package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.pojo.User;
import com.sun.jdi.BooleanType;

import java.lang.reflect.*;
import java.util.List;

public class DefaultSqlSession implements SqlSession{

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration=configuration;
    }

    @Override
    public <E> List<E> selectList(String statementId, Object... params) {
        SimpleExecutor simpleExecutor=new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        Object obj = simpleExecutor.query(configuration, mappedStatement, params);
        return (List<E>) obj;
    }

    @Override
    public <T> T selectOne(String statementId, Object... params) {
        List<Object> objects=selectList(statementId,params);
        if(objects.size()==1){
            return (T)objects.get(0);
        }
        return null;
//        throw new RuntimeException("查询结果为空或返回结果过多");
    }

    @Override
    public boolean execute(String statementId, Object... params) {
        SimpleExecutor simpleExecutor=new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        Object b = simpleExecutor.query(configuration, mappedStatement, params);
        return (boolean) b;
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        //使用jdk动态代理为Dao接口生成代理对象，并返回
        Object proxyInstatnce= Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
               //底层都还是去执行JDBC代码  根据不同情况，来调用selectList或者selectOne
               //准备参数：1.statmentid:sql语句的唯一标识：namespace.id=接口全限定名.方法名
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();
                String statementId=className+"."+methodName;
                //准备参数2：params:args
                //获取返回值
                Type genericReturnType = method.getGenericReturnType();
                //判断是否进行了泛型类型参数化
                if(genericReturnType instanceof ParameterizedType){
                    List<Object> objects = selectList(statementId, args);
                    return objects;
                }else{
                    Class<?> returnType = method.getReturnType();
                    if(returnType==User.class){
                        return selectOne(statementId,args);
                    }
                    return execute(statementId,args);
                }

            }
        });
        return (T) proxyInstatnce;
    }
}
